WhatsApp users in China on Tuesday reported problems with the messaging app, sparking fears that the service could have been blocked by authorities following Chinese Nobel Peace laureate and dissident Liu Xiaobo's death.

People who tried to use the app said they were unable to send videos and photos and also had problems sending text-based messages, the New York Times reported.

Some users reported that the only way to use the app properly was through tools that circumvent the country's strict internet blocks, dubbed the Great Firewall.

"According to the analysis that we ran today on WhatsApp's infrastructure, it seems that the Great Firewall is imposing censorship that selectively targets WhatsApp functionalities," said Nadim Kobeissi, an applied cryptographer.

Kobeissi said it was not clear whether the targeted censorship of videos and photos was intentional, or if it was just a prelude to a more complete block of WhatsApp in the coming days.

In recent weeks, the government has appeared to increase its grip, an online crackdown fed by a perfect storm of politically sensitive news, important upcoming events, and a new cybersecurity law that went into effect last month, said the report.

The problems have led users to speculate that the Chinese government could have partially blocked WhatsApp, which offers users more privacy from spying authorities than alternative apps because it uses end-to-end encryption. 

It comes after reports earlier this week that Chinese authorities were intercepting and deleting mobile app WeChat messages commemorating Liu Xiaobo, the Nobel laureate who died after years of imprisonment in the country. 

Citizen Lab, a monitoring project at the University of Toronto, Canada, said images related to the renowned dissident were blocked in private messages, group chats and on WeChat's Moments feed following his death. 

"Chinese social media companies receive greater government pressure around critical or sensitive events," said Citizen Lab. "Our findings document a significant shift in censorship after Liu Xiaobo's death."

China also appears to have blocked all results on Liu from the Weibo search engine.